Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence of a display screen or portionthereof with transitional graphical user interface showing our newdesign; and,

FIG. 2 is the second image thereof.

The dashed broken line perimeter in the drawings illustrates a displayscreen or portion thereof and forms no part of the claimed design. Theremaining dashed broken lines in the drawings illustrate portions of thegraphical user interface that form no part of the claimed design.

The stipple shading in FIG. 2 depicts a contrast of appearance.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-2. The process or period in whichone image transitions into another image forms no part of the claimeddesign.

CLAIM The ornamental design for a display screen or portion thereof withtransitional graphical user interface, as shown and described.